Massive machine-type communications (mMTC) is an evolving 5G use-case, expected to serve around \(10^6\)  devices per square kilometer [1]}.
The users in mMTC applications are sporadically active and transmit short packets to a central base station (BS) [2]}.
Grant-free random access (GFRA) protocols are appropriate in mMTC applications since they incur a low control and signaling overhead [3]}, [4]}.
Typically, in these protocols, users transmit packets (consisting of a header containing pilot symbols followed by the data payload) by randomly accessing resource elements (REs).
Since the length of orthogonal pilots scales linearly with the number of users, the overhead of assigning orthogonal pilots becomes prohibitively expensive.
Thus, pilot contamination is inevitable due to the use of non-orthogonal pilots, and has to be accounted for while analyzing the performance of GFRA protocols for mMTC.
